[libvirt] [PATCH] docs: expand the man page text for virsh setmaxmem

[Matthias Bolte]

2011/1/27 Justin Clift <jclift at redhat.com>:
> Addresses BZ # 622534:
>
>  https://bugzilla.redhat.com/show_bug.cgi?id=622534
> ---
>  tools/virsh.pod |   17 ++++++++++++++---
>  1 files changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/tools/virsh.pod b/tools/virsh.pod
> index 4e8b295..0d37512 100644
> --- a/tools/virsh.pod
> +++ b/tools/virsh.pod
> @@ -584,9 +584,20 @@ update the XML <currentMemory> element.
>
>  =item B<setmaxmem> I<domain-id> B<kilobytes>
>
> -Change the maximum memory allocation limit in the guest domain. This should
> -not change the current memory use. The memory limit is specified in
> -kilobytes.
> +Change the maximum memory allocation limit for an inactive guest domain.
> +
> +This command works for at least the Xen and vSphere/ESX hypervisors,
> +but not for QEMU/KVM.
> +
> +Some hypervisors require a larger granularity than kilobytes, rounding down
> +or rejecting requests that are not an even multiple of the desired amount.
> +vSphere/ESX is one of these, requiring the parameter to be evenly divisible
> +by 4MB.  For example with vSphere/ESX, 262144 (256MB) is valid as it's a
> +multiple of 4MB; 263168 (257MB) is not valid as it's not a multiple of 4MB;
> +266240 (260MB) is also valid, as it's a multiple of 4MB.
>

Well, currently this is true. But I'm preparing a patch that makes
libvirt round memory/storage request up instead of down when dividing
it for a larger granularity. That way you'll get at least what you
requested.

I basically applied the pattern we started to use in commit "storage:
Round up capacity for LVM volume creation" to all places where it
applies. I also removed the strict checks from the ESX driver. This
means that the ESX driver will automatically round 257MB up to 260MB
instead of reporting an error.

I didn't post the patch yet, as it isn't finished yet.

When my patch gets accepted your patch needs some small tweaks :)

Matthias